People are generally aware of the most common causes of hallucinations, like schizophrenia and a really high fever. But lesser known are the more rare causes; here are six you probably haven't heard about.

Spiritual People More Likely to Have Mental Health Problems

According to a new study, there might be an association between spirituality and mental disorders.

The study was conducted by a team of researchers led by Professor Michael King, from University College London.

"Our main finding is that people who had a spiritual understanding of life had worse mental health than those with an understanding that was neither religious nor spiritual," wrote King and his colleagues, reported The Telegraph.

The study was based on a survey of more than 7,000 people in England. Researchers found a group of people who claimed that they were not religious but were spiritual. This particular group was found to be more vulnerable to mental illness.

About 35 percent of the study participants said that they were religious; 46 percent said that they were neither religious nor spiritual while 19 percent said that they were spiritual but not religious.

The spiritual group people were 50 percent more likely to have a generalized anxiety disorder and a 72 percent more likely to have a phobia. These people also had 77 percent higher odds of using drugs and were at 33 percent higher risk of a neurotic disorder.

"People who have a spiritual understanding of life in the absence of a religious framework are vulnerable to mental disorder," researchers conclude.

However, according to a study analysis on NHS, the main limitation of the study is that it doesn't prove cause and effect relationship. And, although it is tempting to say that spiritual people may develop mental health problems, it is equally valid that these people took the spiritual way to find alternative solutions to their problems.